The present invention generally relates to systems for containing a burst impeller or impeller fragments and, more particularly, to containment systems that include a vaneless diffuser.
A prior art compressor 30, as depicted in FIG. 1, can include one or more impellers 31 in contact with a rotating shaft 32. A housing structure 35, which may comprise one or more members fastened together by housing fasteners 36, can enclose the impeller 31. The housing structure 35 can include a radially outer wall 33, as depicted in FIGS. 1 and 2. In some circumstances, due to, for example, corrosion, defect or fatigue, the impeller 31 can fracture and burst from the shaft 32 during operation. In the event of an impeller fracture, the impeller 31 may break into two, three or more large fragments that are thrown radially outward from the shaft 32, through a diffuser 37 and toward the radially outer wall 33 due to centrifugal force. Fragments of the impeller 31 can penetrate the thin-walled portions of the radially outer wall 33. The burst impeller fragments can form a hole 34 through the radially outer wall 33, as depicted in FIG. 3. The hole 34 may allow the impeller fragments to escape from the housing 35. To minimize or prevent damage to the aircraft, systems for containing the burst impeller fragments have been described in the prior art.
U.S. Pat. No. 6,695,574 discloses an energy absorber and deflection device for deflecting engine debris fragments from a core of a gas turbine engine. The device includes a deflection plate radially spaced from and adapted to cover any rotating component of the engine. The disclosed device may be used to contain fan blade fragments, rotor fragments, broken shaft fragments, compressor fragments, turbine blade fragments or turbine rotor fragments. Unfortunately, the deflection plate adds weight to and increases the envelope of the engine. Although the described device may be used to contain engine debris, it is not suitable for some applications due to envelope and weight restrictions.
U.S. Pat. No. 6,224,321 discloses an impeller containment system. The described system utilizes a catcher extending from a shroud plate adjacent to the impeller, which engages with a snubber formed as a unitary part of the impeller. The catcher and snubber cooperate to restrain a burst impeller or impeller fragments to their shortest radial distance from their point of burst. The described system also includes a shroud, which circumferentially surrounds the impeller and a diffuser, which circumferentially surrounds the radial tip portions of the impeller. The back plate of the described containment system has a catcher groove and flange and the impeller has a snubber groove and flange. These grooves and flanges increase the complexity of the compressor components. The described system adds further complexity by including a bayonet flange on the impeller shroud that is designed to interact with a recessed grooved portion of the diffuser.
Other fragment containment methods have included increasing the strength of the shroud by increasing the thickness of the housing walls. Unfortunately, increasing wall thickness increases system weight.
For some compressors, the inclusion of vaned diffusers can provide sufficient fragment containment. Unfortunately, vaned diffusers are not suitable for all compressor designs.
As can be seen, there is a need for improved containment systems. Additionally, containment systems are needed that do not adversely affect the weight and envelope of the engine/machine. Further, simple containment systems are needed that do not require complex component designs. Moreover, containment systems are needed for compressor designs that do not include vaned diffusers.